Communication apparatus and control information receiving method

ABSTRACT

In a base station, a control unit and a data size regulation unit control the data size of downstream assignment control data and upstream assignment control data in the PDCCH signal based on the communication format used between the base station and a terminal, the number of base station antennas (M) (nonnegative number), the number of terminal antennas (N) (nonnegative number), the bandwidth of the downstream band, and the bandwidth of the upstream band. Specifically, the control unit determines it is unnecessary to adjust the aforementioned data size when the selected communication format is first established between multiple antennas and when where there are multiple for one of M and N and only one for the other. The quality of downstream assignment control data is prevented from degrading, while preventing the number of blind determinations from increasing on the receiving side of the downstream control channel signal.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation application of application Ser. No. 14/551,763filed Nov. 24, 2014, which is a continuation application of applicationSer. No. 13/131,480 filed May 26, 2011, which is a national stage ofPCT/JP2009/007254 filed Dec. 25, 2009, which is based on JapaneseApplication No. 2008-332127 filed Dec. 26, 2008, the entire contents ofeach of which are incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a radio base station, radio terminal,and channel signal forming method.

BACKGROUND ART

In 3GPP LTE, OFDMA (Orthogonal Frequency Division Multiple Access) isemployed as a downlink communication method. In a radio communicationsystem adopting 3GPP LTE, a base station transmits a synchronizingsignal (synchronization channel: SCH) and a broadcast signal (broadcastchannel: BCH) using prescribed communication resources. A terminal firstsynchronizes with a base station by capturing the SCH. Then, theterminal acquires parameters that are specific to that base station (forexample, a frequency bandwidth) by reading BCH information (seeNon-patent Literature 1, 2 and 3).

Also, after the terminal acquires base station-specific parameters, theterminal sends a connection request to the base station, and, by thismeans, establishes communication with the base station. When necessary,the base station transmits control information to the terminal, withwhich communication has been established, using a PDCCH (PhysicalDownlink Control CHannel).

The terminal performs “blind detection” for a received PDCCH signal.That is, a PDCCH signal includes a CRC (Cyclic Redundancy Check) part,and, at a base station, this CRC part is masked by the terminal ID ofthe target terminal. Thus, until a terminal demasks the CRC part of areceived PDCCH signal with the terminal's terminal ID, the terminalcannot decide whether or not the PDCCH signal is for that terminal. Inthis blind detection, if the result of demasking is that CRC calculationis OK, the PDCCH signal is decided to have been sent for the terminal.

Also, control information sent from a base station includes assignmentcontrol information including information about resources which a basestation allocates to a terminal. A terminal needs to receive bothdownlink assignment control information and uplink assignment controlinformation which have a plurality of formats. Although downlinkassignment control information which a terminal should receive can bedefined in a plurality of sizes depending on the transmitting antennacontrol method and frequency allocation method at a base station, and aterminal identifies the format using this size difference, some of thesedownlink assignment control information formats (hereinafter simplyreferred to as “downlink assignment control information”) and uplinkassignment control information formats (hereinafter simply referred toas “uplink assignment control information”) are transmitted in a PDCCHsignal which has the same size. Downlink assignment control informationand uplink assignment control information which have this sameinformation size include type information of assignment controlinformation (for example, a 1-bit flag). Thus, even if the size of aPDCCH signal including downlink assignment control information and thesize of a PDCCH signal including uplink assignment control informationare the same, a terminal checks type information of assignment controlinformation, and by this means can distinguish between downlinkassignment control information and uplink assignment controlinformation. The PDCCH format to transmit uplink assignment controlinformation is PDCCH format 0, and the PDCCH format to transmit downlinkassignment control information, transmitted in a PDCCH signal being thesame size as uplink assignment control information, is PDCCH format 1A.

However, cases might occur where the information size of uplinkassignment control information determined from the uplink bandwidth(that is, the number of bits required for transmission) and theinformation size of downlink assignment control information determinedfrom the downlink bandwidth differ. To be more specific, if an uplinkbandwidth is small, the information size of uplink assignment controlinformation becomes small, and, if a downlink bandwidth is small, theinformation size of downlink assignment control information becomessmall. If a difference of bandwidth results in a difference ofinformation size like this, by adding zero information to the smallerassignment control information (that is, by performing zero-padding),the size of downlink assignment control information and the size ofuplink assignment control information are made equal. By this means,whether the content is downlink assignment control information or uplinkassignment control information, PDCCH signals have the same size. Thesize adjustment of control information as mentioned above reduces thenumber of times of blind detection at a terminal on the receiving side.

Also, the standardization of 3GPP LTE-advanced has been started torealize much faster communication than 3GPP LTE. 3GPP LTE-advancedsystem (hereinafter referred to as “LTE-A system”) follows 3GPP LTEsystem (hereinafter referred to as “LTE system”). In 3GPP LTE-advanced,to realize an uplink transmission speed of maximum 500 Mbps or greaterand improve uplink frequency use efficiency, MIMO (Multi-InputMulti-Output) in uplink communication is expected to be introduced.Thus, a terminal has multiple transmitting antennas, and controls anuplink transmission weight (that is, precoding vector) and the number ofuplink channel data subject to spatial multiplex (that is, the number ofspatial layers) based on the command of a base station.

Also, to improve uplink frequency use efficiency, studies are underwayto allocate uplink data in the frequency domain discontinuously(hereinafter simply referred to as “discontinuous allocation”). In thiscase, for example, OFDM and clustered DFT-s-OFDMA are applied (seeNon-patent Literature 4). Thus, while conventional LTE only supports acontinuous allocation in a frequency domain because of a limitation ofSC-FDMA, it is possible in an LTE-A system to allocate a high qualitysubcarrier adaptively to a terminal in the frequency domain, so thatuplink frequency use efficiency is expected to be improved.

CITATION LIST Non-Patent Literature NPL 1

-   3GPP TS 36.211 V8.4.0, “Physical Channels and Modulation (Release    8),” September 2008

NPL 2

-   3GPP TS 36.212 V8.4.0, “Multiplexing and channel coding (Release    8),” September 2008

NPL 3

-   3GPP TS 36.213 V8.4.0, “Physical layer procedures (Release 8),”    September 2008

NPL 4

-   3GPP TSG RAN WG1 #54bis document RI-083658 “Uplink multiple access    schemes for LTE-A” LGE, September 2008

SUMMARY OF INVENTION Technical Problem

If a downlink frequency bandwidth and an uplink frequency bandwidth arealmost equal, as for the above mentioned format pair, the informationsize of uplink assignment control information and downlink assignmentcontrol information is nearly the same. Thus, zero-padding is rarelyperformed. By contrast with this, if a downlink bandwidth is much largerthan an uplink bandwidth, as for this pair, a lot of zero information isadded to the smaller uplink assignment control information until theinformation size of this uplink assignment control information becomesequal to the information size of downlink assignment controlinformation. Also, if an uplink bandwidth is much larger than a downlinkbandwidth, as for this pair, a lot of zero information is added to thesmaller downlink assignment control information until the informationsize of this downlink assignment control information becomes equal tothe information size of uplink assignment control information. However,zero-padding is performed for size adjustment, and zero informationitself carries no meaning. As a result, assignment control informationincludes fundamentally unnecessary signal, so that if overall power isfixed, power per information bit fundamentally necessary declines.

Also, to avoid zero-padding, it is possible to apply a method of makingthe information sizes of uplink assignment control information anddownlink assignment control information of the format pair different.However, in this case, a terminal side has to perform blind detectionseparately for two pieces of assignment control information havingdifferent numbers of information bits. Thus, in a terminal, the numberof times of blind detection increases, and, accompanying this, theincrease of circuit scale becomes a problem.

Also, if MIMO and discontinuous allocation are applied to uplink, it isnecessary to indicate by a downlink control signal which transmissionweight, (that is, precoding vector), a base station uses to transmituplink channel data for a terminal, MCS for each layer on a spatialaxis, and a command of discontinuous frequency allocation. Thus, whilein an uplink of conventional LTE, there is no idea of MIMO anddiscontinuous allocation, so that only Format 0 is used to reportresource allocation for uplink channel data, in an uplink of an LTE-Asystem, in accordance with the introduction of a spatial multiplexing, adirectional transmission of MIMO, and discontinuous allocation, multipleformats for reporting uplink channel data resource other than Format 0are necessary. This shows that the number of formats in a downlinkcontrol signal which should be performed blind detection on a terminalside increases, and a terminal will become complicated, so that somekind of technique is required.

It is therefore an object of the present invention to provide a radiobase station, radio terminal, and channel signal forming method that,when communication is performed using a downlink band and an uplink bandbetween a radio terminal that has N transmission antenna ports (N is anatural number) and a radio base station that has M antenna ports (M isa natural number), prevent the number of times of blind detection in aradio terminal, which is on the receiving side of a downlink controlchannel signal from increasing, and reduce the frequency of performingsize adjustment process to downlink assignment control information oruplink assignment control information, so that it is possible to preventthe quality of downlink assignment control information or uplinkassignment control information from degrading.

Solution of Problem

A radio base station according to the present invention has Mtransmission antenna ports (M is a natural number), communicates with aradio terminal having N transmission antenna ports (N is a naturalnumber) using a downlink band and an uplink band, and employs aconfiguration having: a forming section that forms a downlink channelsignal including downlink assignment control information in a downlinkband and uplink assignment control information in an uplink band; and asize control section that adjusts an information size of the downlinkassignment control information and uplink assignment control informationincluded in the formed downlink channel signal, based on a communicationscheme applied between the radio base station and the radio terminal, anumber M of transmitting antenna ports of the radio base station, anumber N of transmitting antenna ports of the radio terminal, abandwidth of the downlink band, and a bandwidth of the uplink band.

A radio terminal according to the present invention has N transmissionantenna ports (N is a natural number), communicates with a radio basestation having M transmission antenna ports (M is a natural number)using a downlink band and an uplink band, and employs a configuration tohave: a radio reception section that receives a downlink channel signalincluding downlink assignment control information in a downlink band anduplink assignment control information in an uplink band; a determiningsection that determines the basic information size used for a receivingprocess of the downlink channel signal; and a channel signal receivingprocess section that receives a channel signal based on the basicinformation size, and, in this radio terminal, the determining sectiondetermines that the basic information size based on a communicationscheme applied between the radio terminal and the radio base station, anumber M of transmitting antenna ports of the radio base station, anumber N of transmitting antenna ports of the radio terminal, abandwidth of the downlink band, and a bandwidth of the uplink band.

A channel signal forming method according to the present invention formsa downlink channel signal used to control communication carried outbetween a radio terminal that has N transmission antenna ports (N is anatural number) and a radio base station that has M antenna ports (M isa natural number) using a downlink band and an uplink band, and thechannel signal forming method, and includes forming a downlink channelsignal including downlink assignment control information in a downlinkband and uplink assignment control information in an uplink band; andadjusting an information size of the downlink assignment controlinformation included in a downlink channel signal and uplink assignmentcontrol information included in the formed downlink channel signal basedon a communication scheme applied between the radio base station and theradio terminal, a number M of transmitting antenna ports of the radiobase station, a number N of transmitting antenna ports of the radioterminal, a bandwidth of the downlink band, and a bandwidth of theuplink band.

Advantageous Effects of Invention

The present invention provides a radio base station, radio terminal, andchannel signal forming method that, when communication is performedusing a downlink band and an uplink band between a radio terminal thathas N transmission antenna ports (N is a natural number) and a radiobase station that has M antenna ports (M is a natural number), preventthe number of times of blind detection in a radio terminal, which is onthe receiving side of a downlink control channel signal from increasing,and reduce the frequency of performing size adjustment process todownlink assignment control information or uplink assignment controlinformation, so that it is possible to prevent the quality of downlinkassignment control information or uplink assignment control informationfrom degrading.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a format for reporting uplink and downlink channel dataresources:

FIG. 2 shows a format for reporting resource;

FIG. 3 is a block diagram showing a configuration of a base stationaccording to the embodiment of the present invention;

FIG. 4 is a block diagram showing a configuration of a terminalaccording to the embodiment of the present invention;

FIG. 5 shows operations of a base station and a terminal; and

FIG. 6 shows operations of a base station and a terminal.

DESCRIPTION OF EMBODIMENTS

As mentioned above, in an uplink of LTE-A system, in accordance with theintroduction of spatial multiplexing, directional transmission of MIMOcommunication (hereinafter simply referred to as “directionaltransmission”), and discontinuous allocation, for example, as shown inFIG. 1, multiple formats (Format 0A/0B/0C) for reporting uplink channeldata resources, other than Format 0, are necessary.

Here, the present inventors have taken note of the fact that in adownlink channel of LTE, spatial division multiplexing (SDM),directivity control (a precoding matrix indicator report (PMI report)),and frequency discontinuous allocation already exist. That is to say, itis likely that, following an LTE system, a downlink channel of an LTE-Asystem uses the same formats (Format 1B/1/2) for reporting downlinkchannel data resource as in an LTE system. Also, the present inventorshave taken note of the fact that the information sizes of Format0A/0B/0C are the same as the information sizes of Format 1B/1/2 wherethe communication mode is applied.

Thus, the present inventors have found out that if the similar sizeformats are made as a set (see FIG. 2) like the relationship betweenFormat 0 and Format 1A in LTE, and information size adjustment such aspadding is performed to the set, a single blind detection on thereceiving side can decode two formats at the same time.

Also, the present inventors have found out that part of these sets donot require information size adjustment. Furthermore, the presentinventors have found out that the part of sets and other sets can bedistinguished based on the number of transmitting antenna ports in abase station and the number of transmitting antenna ports in a terminal.

The present inventors have found out that by adjusting the informationsize of downlink assignment control information, included in a downlinkchannel signal, and uplink assignment control information, based on thenumber M of transmitting antenna port of a base station, the number N oftransmitting antenna port of a terminal, a downlink bandwidth, and anuplink bandwidth, it is possible to prevent the number of times of blinddetection in a radio terminal from increasing, and to prevent thequality of downlink assignment control information from degrading.

Here, “antenna port” means a logical antenna (antenna group) formed byone or multiple physical antennas. Thus, an antenna port is not limitedto mean one physical antenna, and may be such as an array antenna formedby multiple antennas. For example, in non-patent literature 1, althoughhow many physical antennas constitute an antenna port is not defined, anantenna port is defined as a minimum unit whereby a base station cantransmit a different reference signal. An antennal port is also definedas a minimum unit of precoding vector weighting multiplication.

In the following embodiments, for ease of explanation, a case will bedescribed where an “antenna port” and a physical antenna are associatedon a one-by-one basis.

Now, an embodiment of the present invention will be explained in detailwith reference to the accompanying drawings.

FIG. 3 is a block diagram showing a configuration of base station 100according to an embodiment of the present invention. In FIG. 3, basestation 100 includes control section 101, PDCCH generating section 102,information size adjusting section 103, CRC (Cyclic Redundancy Check)adding section 104, modulating sections 105 and 106, SCH/BCH generatingsection 107, precoding section 108, multiplexing section 109, IFFTsection 110, CP adding section 111, RF transmission section 112, antenna113, RF reception section 114, CP removing section 115, FFT section 116,extracting section 117, signal combining section 118, IDFT section 119,and data reception section 120.

Control section 101 generates control information (including uplinkassignment control information and downlink assignment controlinformation).

With information size adjusting section 103, control section 101includes a function as an information size control means to adjust theinformation size of downlink assignment control information and uplinkassignment control information included in a PDCCH signal. Toinformation size adjusting section 103, control section 101 outputsinformation according to the communication scheme applied betweencontrol section 101 and terminal 200 of a communication party which willbe described later. The presumed communication schemes here are the fourpatterns shown in FIG. 1, namely communication without directivitycontrol based on a command from a base station, directionalcommunication based on a command from a base station, communication bydiscontinuous allocation without directivity control based on a commandfrom a base station, communication by discontinuous allocation beingdirectional communication on spatial multiplexing based on a commandfrom a base station. In communication without directivity control basedon a command from a base station Format 1A and Format 0 are a pair. Indirectional communication based on a command from a base station, Format1 B and Format 0A are a pair. In communication by discontinuousallocation without directivity control based on a command from a basestation, Format 1 and Format 0B are a pair. In communication ofdiscontinuous allocation information, which is directional communicationby spatial multiplexing based on a command from a base station, Format 2and Format 0C are a pair.

Specifically, for the pair of Format 1A and Format 0 and the pair ofFormat 1 and Format 0B, control section 101 outputs information sizecomparing information showing the difference in size between theinformation size of downlink assignment control information determinedfrom the downlink frequency bandwidth and the information size of uplinkassignment control information determined from the corresponding uplinkfrequency bandwidth, to information size adjusting section 103.

For the pair of Format 1B and Format 0A and the pair of Format 2 andFormat 0C, control section 101 outputs information size comparinginformation showing the difference in size between the information sizeof downlink assignment control information determined from the downlinkfrequency bandwidth and from the number of antennas of base station 100,and the information size of uplink assignment control informationdetermined from the corresponding uplink frequency bandwidth and thenumber of antennas of terminal 200, to information size adjustingsection 103.

Also, control section 101 generates padding control information based onthe number of transmitting antennas of base station 100 and the numberof transmitting antennas of terminal 200, and outputs the paddingcontrol information to information size adjusting section 103.Specifically, if the number of transmitting antennas of terminal 200 towhich base station 100 transmits a control signal is one, controlsection 101 generates padding control information not to perform paddingfor Format 1B and Format 2, and if the number of transmitting antennasof base station 100 is one, control section 101 generates paddingcontrol information not to perform padding for Format 0A and Format 0C.

PDCCH generating section 102 receives control information generated incontrol section 101, and generates a PDCCH signal to be sent in eachdownlink frequency band, based on the control information.

Information size adjusting section 103 receives the control information,information size comparing information, and padding control informationgenerated in control section 101. Based on control information,information size comparing information, and padding control information,information size adjusting section 103 adjusts the information size ofuplink assignment control information and downlink assignment controlinformation included in a PDCCH signal received from PDCCH generatingsection 102.

Specifically, based on padding control information, information sizeadjusting section 103 determines whether or not a PDCCH signal subjectto information size adjustment requires padding.

If information size adjusting section 103 determines, based on paddingcontrol information, that information size needs to be coordinatedbetween uplink assignment control information and downlink assignmentcontrol information, for the pair of Format 1A and Format 0 and the pairof Format 1 and Format 0B, information size adjusting section 103 usesthe larger one of the information size of downlink assignment controlinformation determined from the downlink frequency bandwidth and theinformation size of uplink assignment control information determinedfrom the corresponding uplink frequency bandwidth as a size adjustmentreference, and, based on this size adjustment reference, informationsize adjusting section 103 adjusts the information size of assignmentcontrol information.

If information size adjusting section 103 determines, based on paddingcontrol information, that information size between uplink assignmentcontrol information and downlink assignment control information needs tobe coordinated, for the pair of Format 1B and Format 0A and the pair ofFormat 2 and Format 0C, information size adjusting section 103 uses thelarger one of the information size of downlink assignment controlinformation determined from the downlink frequency bandwidth and thenumber of antennas of a base station and the information size of uplinkassignment control information determined from the corresponding uplinkfrequency bandwidth and the number of antennas of a terminal as a sizeadjustment reference, and, based on this size adjustment reference,information size adjusting section 103 adjusts the information size ofassignment control information.

On the other hand, if information size adjusting section 103 determines,based on padding control information, that information size betweenuplink assignment control information and downlink assignment controlinformation does not need to be coordinated, for the pair of Format 0Aand Format 1 B and the pair of Format 2 and Format 0C, for downlinkassignment control Information (that is, Format 1B and Format 2),information size adjusting section 103 uses the information size ofdownlink assignment control information determined from the downlinkfrequency bandwidth and the number of antennas of base station 100 asis, and for uplink assignment control information (that is, Format 0Aand Format 0C), information size adjusting section 103 uses theinformation size of uplink assignment control information determinedfrom the uplink frequency bandwidth and the number of antennas of aterminal as is. That is, an information size adjustment is notperformed. However, as for the pair of Format 1A and Format 0 and thepair of Format 1 and Format 0B, an information size adjustment isperformed as mentioned above.

To be more specific, information size adjusting section 103 includes apadding section (not shown) to adjust the information size of controlinformation by adding zero information to control information. Thispadding section adds zero information to the smaller information sizesuntil the information size of downlink assignment control informationand the information size of uplink assignment control information haveequal information size. To which one of downlink assignment controlinformation and uplink assignment control information zero informationis added is determined based on information size comparing information.

CRC adding section 104 adds a CRC bit to a size adjusted PDCCH signal ininformation size adjusting section 103, and then masks the CRC bit witha terminal ID. Then, CRC adding section 104 outputs the masked PDCCHsignal to modulating section 105.

Modulating section 105 modulates a PDCCH signal input from CRC addingsection 104, and outputs the modulated PDCCH signal to precoding section108.

Modulating section 106 modulates input transmission data (downlinkdata), and outputs the modulated transmission data signal to precodingsection 108.

SCH/BCH generating section 107 generates a SCH and BCH, and outputs thegenerated SCH and BCH to precoding section 108.

Precoding section 108 applies a weight for a transmission signal foreach terminal, on a per antenna 113 basis, based on precodinginformation, that is, based on transmission weight control information,provided from control section 101. This precoding process is performedfor the PDCCH signal input from modulating section 105, the data signal(that, is a PDSCH signal) input from modulating section 106, and the SCHand BCH input from SCH/BCH generating section 107. The weight (PrecodingMatrix Indicator: PMI) used for this precoding for downlink assignmentcontrol information and SCH/BCH is determined in advance between theterminal side and the base station side. Thus, terminal 200 receivesdownlink control information according to the weight. The PMI fordownlink channel data is reported to each terminal 200, individually, bydownlink assignment control information.

Multiplexing section 109 multiplexes the PDCCH signal after precodingprocessing, a data signal, and a SCH and BCH. Based on the terminal IDinput from control section 101 and downlink assignment controlinformation associated with the terminal ID, multiplexing section 109maps a data signal (a PDSCH signal) for terminal 200 associated with theterminal ID to a downlink component band.

Also, multiplexing section 109 maps the PDCCH signal after precodingprocessing, to the resource region allocated for a PDCCH.

IFFT section 110 converts a multiplex signal into a time waveform, andCP adding section 111 acquires an OFDM signal by adding a CP to thistime waveform.

RF transmission section 112 performs a transmission radio process (suchas up-conversion and a digital-to-analog (D/A) conversion) to an OFDMsignal input from CP adding section 111, and transmits the resultthrough antenna 113. Then, an OFDM signal including assignment controlinformation is sent.

RF reception section 114 performs a receiving radio process (such as adown-conversion and an analog-to-digital (A/D) conversion) to a receivedradio signal which is received in a receiving band through antenna 113,and outputs the received signal to CP removing section 115.

CP removing section 115 removes the CP from the received signal, and FFTsection 116 converts the received signal, from which the CP has beenremoved, into a frequency domain signal.

Based on uplink assignment control information input from controlsection 101, extracting section 117 extracts uplink data from afrequency domain signal input from FFT section 116. Antenna 113, RFreception section 114, CP removing section 115, and FFT section 116 areset double in here. Thus, extracting section 117 performs an extractprocessing for antenna 113 and the same number of streams.

Based on precoding information (that is, transmission weight controlinformation used in terminal 200) used by uplink data indicated fromcontrol section 101, signal combining section 118 combines a signaloutput from extracting section 117 by using a technique such as MRC orMMSE. Therefore, the SINR of a received signal improves.

IDFT (Inverse Discrete Fourier Transform) section 119 converts theextracted signal into a time domain signal and outputs the time domainsignal to data reception section 120.

Data reception section 120 decodes the time domain signal input fromIDFT section 119. And data reception section 120 outputs decoded uplinkdata as received data.

FIG. 4 is a block diagram showing the configuration of terminal 200according to an embodiment of the present invention. In FIG. 4, terminal200 includes antenna 201, RF reception section 202, CP removing section203, FFT section 204, frame synchronization section 205, demultiplexingsection 206, signal combining section 207, broadcast signal receptionsection 208, information size determination section 209, PDCCH receptionsection 210, format determination section 211, PDSCH reception section212, modulating section 213, DFT section 214, frequency mapping section215, precoding section 216, IFFT section 217, CP adding section 218, andRF transmission section 219.

RF reception section 202 performs a receiving radio process (such as adown-conversion and an analog-to-digital (A/D) conversion) to a receivedradio signal (in this case, an OFDM signal) which is received in areceiving band through antenna 201, and outputs the received signal toCP (Cyclic Prefix) removing section 203.

CP removing section 203 removes the CP from the received signal, and FFT(Fast Fourier Transform) section 204 converts the received signal, fromwhich the CP has been removed, into a frequency domain signal. Thisfrequency domain signal is output to frame synchronization section 205.

While searching for a SCH included in a signal input from FFT section204, frame synchronization section 205 establishes synchronization(frame synchronization) with base station 100. Also, framesynchronization section 205 acquires a cell ID associated with asequence used for a SCH (a SCH sequence). That is, the same process as anormal cell search is performed in frame synchronization section 205.Also, to demultiplexing section 206, frame synchronization section 205outputs frame synchronization timing information showing a framesynchronization timing, and the signal input from FFT section 204.

Based on frame synchronization timing information input from framesynchronization section 205, demultiplexing section 206 demultiplexesthe signal input from frame synchronization section 205 into a broadcastsignal (that is, a BCH), a control signal (that is, a PDCCH signal), anda data signal (that is, a PDSCH signal). Demultiplexing section 206receives information about a downlink component band from broadcastsignal reception section 208, and extracts a PDCCH signal on a perdownlink component band basis based on this information.

Based on PMI information of PDSCH output from format determinationsection 211, a broadcast signal determined in advance by the terminalside and the base station side, and PMI information of PDCCH, signalcombining section 207 combines the broadcast signal, the PDCCH, and thePDSCH, demultiplexed from a received component in each antenna 201 ofterminal 200.

Broadcast signal reception section 208 reads the contents of a BCH inputfrom signal combining section 207, and acquires information about aconfiguration of a downlink band and uplink band of base station 100.Broadcast signal reception section 208 acquires, for example, thebandwidth of uplink component band, the bandwidth of downlink componentband, and information about their associations. Broadcast signalreception section 208 outputs the acquired BCH information toinformation size determination section 209, PDCCH reception section 210,and format determination section 211.

Information size determination section 209 receives a PDCCH signal fromsignal combining section 207, and determines the basic information sizeto perform blind detection on this PDCCH signal. For the pair of Format1A and Format 0 and the pair of Format 1 and Format 0B, this basicinformation size is determined from the downlink frequency bandwidthreceived from broadcast signal reception section 208 and thecorresponding uplink frequency bandwidth, and, for the pair of Format 1Band Format 0A and the pair of Format 2 and Format 0C, this basicinformation size is determined from the number of transmitting antennasof base station 100, the downlink frequency bandwidth received frombroadcast signal reception section 208, the corresponding uplinkfrequency bandwidth, and the number of transmitting antennas of terminal200.

Specifically, if both base station 100 and terminal 200 have multipleantennas, for the pair of Format 1A and Format 0 and the pair of Format1 and Format 0B, information size adjusting section 209 uses the largerone of the information size of downlink assignment control informationdetermined from the downlink frequency bandwidth and the informationsize of uplink assignment control information determined from thecorresponding uplink frequency bandwidth as a size adjustment reference,and, based on this size adjustment reference, information size adjustingsection 209 adjusts the information size of assignment controlinformation. For the pair of Format 1B and Format 0A and the pair ofFormat 2 and Format 0C, information size adjusting section 209 uses thelarger one of the information size of downlink assignment controlinformation determined from the downlink frequency bandwidth and thenumber of antennas of base station 100 and the information size ofuplink assignment control information determined from the uplinkfrequency bandwidth and the number of antennas of a terminal as a sizeadjustment reference, and, based on this size adjustment reference,information size adjusting section 209 adjusts the information size ofassignment control information.

On the other hand, if the number of antennas of terminal 200 is one,information size adjusting section 209 uses the information size ofdownlink assignment control information (that is, Format 1B and Format2) determined from the downlink frequency bandwidth and the number ofantennas of base station 100 as is, for the pair of Format 0A and Format1B and the pair of Format 2 and Format 0C.

Furthermore, if the number of antennas of base station 100 is one,information size adjusting section 209 uses the information size ofuplink assignment control information (that is, Format 0A and Format 0C)determined from the uplink frequency bandwidth and the number ofantennas of terminal 200 as is, for the pair of Format 0A and Format 1Band the pair of Format 2 and Format 0C. That is, an information sizeadjustment is not performed. However, for the pair of Format 1A andFormat 0 and the pair of Format 1 and Format 0B, an information sizeadjustment as mentioned above is performed.

Information size determination section 209 outputs information about thedecided basic information size and the PDCCH signal associated with thisinformation to PDCCH reception section 210.

PDCCH reception section 210 performs blind detection for a PDCCH signalbased on the basic information size decided in information sizedetermination section 209.

That is, PDCCH reception section 210 specifies the CRC bit part by usingthe basic information size (payload size) decided in information sizedetermination section 209. Next, after demasking the specified CRC bitpart by the terminal ID of terminal 200, if a CRC calculation result is“OK” with respect to the whole PDCCH signal, PDCCH reception section 210decides that the PDCCH signal is a PDCCH signal transmitted for terminal200. Thus, the PDCCH signal decided to be received by terminal 200 isoutput to format determination section 211.

Based on type information of assignment control information included ina PDCCH signal received from PDCCH reception section 210, formatdetermination section 211 decides which one is uplink assignment controlinformation or downlink assignment control information between theformat pair having the same size. If format determination section 211identifies uplink assignment control information, format determinationsection 211 outputs uplink assignment control information included inthe PDCCH signal to frequency mapping section 215. Also, if formatdetermination section 211 identifies downlink assignment controlinformation, format determination section 211 outputs downlinkassignment control information included in the PDCCH signal to PDSCHreception section 212.

Based on downlink assignment control information input from formatdetermination section 211, PDSCH reception section 212 extracts receiveddata from the PDSCH signal input from signal combining section 207.

Modulating section 213 modulates transmission data and outputs aresulting modulated signal to DFT (Discrete Fourier Transform) section214.

DFT section 214 converts a modulated signal input from modulatingsection 213 into a frequency domain, and outputs a resulting pluralityof frequency components to frequency mapping section 215.

In accordance with uplink assignment control information input fromformat determination section 211, frequency mapping section 213 maps aplurality of frequency components input from DFT section 214, on a PUSCHplaced in an uplink component band.

Precoding section 216 determines a transmission weight, that is aprecoding vector, to set upon transmission from PMI information includedin uplink assignment control information, and maps the transmission dataon the stream associated with each antenna 201.

IFFT section 217 converts each stream being frequency components into atime domain waveform, and CP adding section 218 adds a CP to the timedomain waveform.

RF transmission section 219 performs a transmission radio process (suchas an up-conversion and a digital-to-analog (D/A) conversion) to asignal with a CP, and transmits the result through antenna 201.

An operation of base station 100 and terminal 200 having the abovementioned configuration will be described. As mentioned above, fourcommunication schemes are prepared between base station 100 and terminal200. That is, there are four patterns: communication scheme 1,communication without directivity control based on a command from a basestation; communication scheme 2, directional communication based on acommand from a base station; communication scheme 3, communication bydiscontinuous allocation without directivity control based on a commandfrom a base station; and communication scheme 4, communication bydiscontinuous allocation being directional communication on spatialmultiplexing based on a command from a base station. As for informationsize control in base station 100 and terminal 200, basically,communication without directivity control based on a command from a basestation and communication by discontinuous allocation withoutdirectivity control based on a command from a base station form onegroup based on the same rule, and directional communication based on acommand from a base station and communication by discontinuousallocation being directional communication on spatial multiplexing basedon a command from a base station form the other group. Thus, to avoidcomplicated explanation, selecting one from each group, communicationscheme 1, which is communication without directivity control based on acommand from a base station, and communication scheme 2, which isdirectional communication based on a command from a base station, willbe described.

If base station 100 or terminal 200 has only one transmitting antennaport, in communication scheme 1, one antenna port is used fortransmitting. Also, if base station 100 or terminal 200 has multipletransmitting antenna ports, in communication scheme 1, diversitytransmission, determined in advance between base station 100 andterminal 200, is performed. Thus, an antenna selecting diversitytransmission which performs communication by selecting one of multipletransmitting antenna ports, STBC, SFBC (see Non-patent Literature 1, 2and 3), so-called “open loop transmission diversity control,” areperformed.

In base station 100, based on the number M (M is a natural number) oftransmitting antennas which are available for the terminal, and thenumber N (N is a natural number) of transmitting antennas which areavailable for terminal 200, control section 101 determines whether theinformation sizes of downlink assignment control information and uplinkassignment control information included in a PDCCH signal need to beadjusted or not.

As shown in FIG. 5, if M and N are both greater than one (in this case,M=N=2), in both communication scheme 1 and communication scheme 2,control section 101 determines that the above information sizeadjustment is necessary.

On the other hand, if one of M and N is greater than one and the otheris one, control section 101 determines that the above mentionedinformation size adjustment is necessary in communication scheme 1, andthe above mentioned information size adjustment is unnecessary incommunication scheme 2.

Information size adjusting section 103 adjusts the information sizes ofdownlink assignment control information and uplink assignment controlinformation included in a PDCCH signal, based on a determination resultof the necessity of information size adjustment in control section 101.

Thus, in communication scheme 1, the above mentioned information sizeadjustment is necessary regardless of the number of antennas. Incommunication scheme 2, if M and N are both greater than one, the abovementioned information size adjustment is necessary, or, if one of M andN is greater than one and the other is one, the above mentionedinformation size adjustment is unnecessary.

Next, information size adjusting section 103 adjusts the informationsizes of downlink assignment control information and uplink assignmentcontrol information included in a PDCCH signal, based on a determinationresult of the necessity of information size adjustment in controlsection 101.

Specifically, in communication scheme 1, information size adjustingsection 103 uses the larger one of the information size of downlinkassignment control information (that is, Format 1A) determined from thedownlink frequency bandwidth and the information size of uplinkassignment control information (that is, Format 0) determined from thecorresponding uplink frequency bandwidth as a size adjustment reference,and, based on this size adjustment reference, information size adjustingsection 103 adjusts the information size of assignment controlinformation.

Even in communication scheme 2, if M and N are both greater than one (inthis case, M=N=2), information size adjusting section 103 uses thelarger one of the information size of downlink assignment controlinformation (that is, Format 1B) determined from the downlink frequencybandwidth and M, and the information size of uplink assignment controlinformation (that is, Format 0A) determined from the correspondinguplink frequency bandwidth and N, as a size adjustment reference, and,based on this size adjustment reference, information size adjustingsection 103 adjusts the information size of assignment controlinformation.

On the other hand, in communication scheme 2, if M is greater than oneand N is one, for downlink assignment control information (that is,Format 1B), information size adjusting section 103 uses the informationsize of downlink assignment control information determined from thedownlink frequency bandwidth and M as is. In this case, uplinkassignment control information is not substantially transmitted. This isbecause when the number N of antennas in terminal 200 is one, it isimpossible to execute, on an uplink channel, communication scheme 2 thatis possible only if the transmitting side has multiple antennas, and itis not even necessary to transmit uplink assignment control information(that is, Format 0A).

Also, in communication scheme 2, if N is greater than one and M is one,for uplink assignment control information (that is, Format 0A),information size adjusting section 103 uses the information size ofuplink assignment control information determined from the uplinkbandwidth and N as is. In this case, downlink assignment controlinformation is not substantially transmitted. This is because when thenumber M of antennas in base station 100 is one, it is impossible toexecute, on a downlink channel, communication scheme 2 that is possibleonly if the transmitting side has multiple antennas, and it is not evennecessary to transmit downlink assignment control information (that is,Format 1B).

As mentioned above, in base station 100, the information size ofdownlink assignment control information included in a downlink channelsignal, and uplink assignment control information are adjusted, based onthe communication scheme, the number M of transmitting antenna ports ofbase station 100, the number N of transmitting antenna ports of terminal200, the bandwidth of a downlink band, and the bandwidth of an uplinkband. Thus, a PDCCH signal which is adjusted an information size istransmitted to terminal 200.

In terminal 200, information size determination section 209 decides thebasic information size when performing blind detection on a receivedPDCCH signal. This basic information size is determined based on thecommunication scheme which is applied between base station 100 andterminal 200, the number M of transmitting antenna ports of base station100, the number N of transmitting antenna ports of terminal 200, thebandwidth of a downlink band, and the bandwidth of an uplink band. Thesepieces of information are shared between base station 100 and terminal200 by communication if a higher layer.

Specifically, in communication scheme 1, information size adjustingsection 209 determines the basic information size based on the largerone of the information size of downlink assignment control information(that is, Format 1A) determined from the downlink frequency bandwidthand the information size of uplink assignment control information (thatis, Format 0) determined from the corresponding uplink bandwidth.

Also, even in communication scheme 2, if M and N are both greater thanone (in this case, M=N=2), information size adjusting section 209determines the basic information size based on the larger one of theinformation size of downlink assignment control information (that is,Format 1B) determined from the downlink frequency bandwidth and M andthe information size of uplink assignment control information (that is,Format 0A) determined from the corresponding uplink frequency bandwidthand N.

On the other hand, in communication scheme 2, if M is greater than oneand N is one, information size adjusting section 209 determines thebasic information size based on the information size of downlinkassignment control information determined from the downlink frequencybandwidth and M.

Also, in communication scheme 2, if N is greater than one and M is one,information size adjusting section 209 determines the basic informationsize based on the information size of uplink assignment controlinformation determined from the uplink frequency bandwidth and N.

As mentioned above, according to the present embodiment, in terminal100, control section 101 and information size adjusting section 103control the information size of downlink assignment control informationand uplink assignment control information included in a PDCCH signal,based on the communication scheme which is applied between base station100 and terminal 200, the number M of transmitting antennas of basestation 100, the number N of transmitting antennas of terminal 200, thebandwidth of a downlink band, and the bandwidth of an uplink band.

Specifically, if the selected communication scheme is possible only ifthe transmitting side has multiple antennas (for example, the abovementioned communication scheme 2 and communication scheme 4) and if oneof M and N is greater than one and the other is one, control section 101determines that the above mentioned information size adjustment isunnecessary.

By this means, the frequency of performing size adjustment process inbase station 100 can be reduced.

On the other hand, if M and N are both greater than one, control section101 determines that the above mentioned information size adjustment isnecessary regardless of the type of communication scheme. In this case,information size adjusting section 103 uses the larger one of theinformation size of downlink assignment control information determinedfrom the downlink frequency bandwidth and M and the information size ofuplink assignment control information determined from the correspondinguplink frequency bandwidth and N as a size adjustment reference, and,based on this size adjustment reference, information size adjustingsection 209 adjusts the information size of assignment controlinformation.

By this means, the sameness of the information size of uplink assignmentcontrol information and the information size of downlink assignmentcontrol information can be kept, it is possible to prevent the number oftimes of blind detection from increasing in terminal 200 on thereceiving side.

According to the above explanation, the information size of each formatpair is determined in relation to the number of transmitting antennas ofbase station 100 and the number of transmitting antennas of terminal200. However, the present invention is not limited to this, and forexample it is possible that base station 100 reports directlyinformation about the method of determining the information size, thatis, the number of effective transmitting antennas on the base stationside and the terminal side, and terminal 200 determines the final basicinformation size based on this report. In this case, as shown in FIG. 6,terminal 200 sets the basic information size, which is calculated basedon the method of determining the information size mentioned in the aboveembodiment, as a default until base station 100 gives a command, andterminal 200 determines the final basic information size according tothe command from base station 100. Thus, for example, if M is 2 and N is2, the upper mode in FIG. 6 becomes a default, and is switched to themiddle mode in which the number of effective transmitting antennas of aterminal is one or the lower mode in which the number of effectivetransmitting antennas of a base station is one by reporting from basestation 100 (that is, signaling of base station 100). Here, it isassumed that both base station 100 and terminal 200 have multipletransmitting antennas. Also, the fact that the number of effectivetransmitting antennas is one here means that one antenna is conditionedto be able to transmit. As this kind of case, for example, a case ispossible where only one transmitting antenna is conditioned to beavailable temporarily because the remaining battery power is low.

According to the above explanation, a base station determines whether ornot information size adjustment of assignment control information isnecessary, based on the number of antenna ports hold by a base stationand a terminal, or the number of effective antenna ports. However, thepresent invention is not limited to this, and, for example, base station100 may report directly to a terminal the method of determininginformation size. Thus, for each communication scheme 1, communicationscheme 2, communication scheme 3, and communication scheme 4, a basestation may report to each terminal 200, on an individual basis, whetheror not an information size adjustment performed between uplinkassignment control information and downlink assignment controlinformation is necessary. In this case, terminal 200 sets the basicinformation size, which is calculated based on the method of determiningthe information size mentioned in the above embodiment, as a defaultuntil base station 100 gives a command, and determines the final basicinformation size according to the command from base station 100.

Also, in FIG. 5 and FIG. 6, a case is described as an example where an“antenna port” and a physical antenna are associated on a one-by-onebasis, but even if “the number of antennas” in FIG. 5 and FIG. 6 isredefined by “the number of antenna ports,” the same effects can begained in the same embodiment.

Although in the above explanation base station 100 transmits a downlinksignal by using a unified downlink frequency band and terminal 200transmits a unified uplink frequency band, the present invention is notlimited to this. Thus, even if so-called carrier aggregation, wheremultiple bands defined in LTE are communicated together, the presentinvention is applicable to each pair of uplink band and downlink band.

Also, in the above explanation, if the number of transmitting antennasof a base station is one, the type information of resource allocation,which is transmitted in the size of the pair of Format 1B and Format 0Aand the pair of Format 2 and Format 0C, always indicates an uplinkallocation signal. That is, the parts associated with the typeinformation of this resource allocation information can be used like aparity bit, or can be used to transmit other kinds of information, ormay be it is possible to increase the power per bit by reducing the bitswhich represent type information, so that can improve power per bit totransport effective information of a PDCCH. The same applies when thenumber of transmitting antennas of a terminal is one.

Embodiment mentioned above explains an example when the presentinvention is performed by hardware, but the present invention can beimplemented with software.

Furthermore, each function block employed in the description of theaforementioned embodiment may typically be implemented as an LSIconstituted by an integrated circuit. These may be individual chips orpartially or totally contained on a single chip. “LSI” is adopted herebut this may also be referred to as “IC,” “system LSI,” “super LSI,” or“ultra LSI” depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSI's, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of an FPGA (FieldProgrammable Gate Array) or a reconfigurable processor where connectionsand settings of circuit cells in an LSI can be regenerated is alsopossible.

Further, if integrated circuit technology comes out to replace LSI's asa result of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application of biotechnology isalso possible.

The disclosure of Japanese Patent Application No. 2008-332127, filed onDec. 26, 2008 including the specification, drawings and abstract, isincorporated herein by reference in their entirety.

INDUSTRIAL APPLICABILITY

A radio base station, radio terminal, and channel signal forming methodof the present invention is useful to prevent the quality of downlinkassignment control information or uplink assignment control informationfrom degrading, by preventing the number of times of blind detection ina radio terminal, which is on the receiving side of a downlink controlchannel signal, from increasing, and by reducing the frequency ofperforming size adjustment process to downlink assignment controlinformation or uplink assignment control information, when communicationis performed using a downlink band and an uplink band between a radioterminal that has N transmission antenna ports (N is a natural number)and a radio base station that has M transmission antenna ports (M is anatural number).

1. An integrated circuit to control a process performed by acommunication apparatus communicating with a base station, the processcomprising: receiving control information, which is one of first controlinformation including downlink resource assignment information andsecond control information including uplink resource assignmentinformation; determining a size of control information, which has beenadjusted by the base station such that when at least one of (i) a numberof antenna port(s) of the communication apparatus and (ii) a number ofantenna port(s) of the base station is one, a size of the second controlinformation with a format including no precoding matrix indicator (PMI)has been adjusted by the base station as being equal to a size of thefirst control information with a format including no PMI, and a size ofthe second control information with a format including the PMI has beenadjusted by the base station as being different from a size of the firstcontrol information; and detecting whether the control information isaddressed to the communication apparatus or not based on the determinedsize of control information and detects whether the control informationis the first control information or the second control information. 2.The integrated circuit according to claim 1, comprising: circuitrywhich, in operation, controls the process; at least one input coupled tothe circuitry, wherein the at least one input, in operation, inputsdata; and at least one output coupled to the circuitry, wherein the atleast one output, in operation, outputs data.
 3. The integrated circuitaccording to claim 1, wherein when a transmission is performed using oneantenna port or when a diversity transmission is performed, the formatincluding no PMI is used.
 4. The integrated circuit according to claim1, wherein the format including no PMI for the second controlinformation is a Format 0, and the format including no PMI for the firstcontrol information is a Format 1A.
 5. The integrated circuit accordingto claim 1, wherein the determining includes determining a larger one ofa size of the first control information with the format including no PMIand a size of the second control information with the format includingno PMI as the size of the control information.
 6. The integrated circuitaccording to claim 1, wherein when a transmission with directivitycontrol is performed, the format including PMI is used for the secondcontrol information.
 7. The integrated circuit according to claim 1,wherein the determining includes determining the size of the secondcontrol information with the format including PMI from an uplinkbandwidth.
 8. The integrated circuit according to claim 1, wherein thedetermining includes determining the size of the first controlinformation with the format including PMI from a downlink bandwidth. 9.The integrated circuit according to claim 2, wherein the at least oneoutput and the at least one input, in operation, are coupled to anantenna.
 10. An integrated circuit embedded to a communication apparatuscommunicating with a base station, the integrated circuit comprising:circuitry, which, in operation: controls reception of controlinformation, which is one of first control information includingdownlink resource assignment information and second control informationincluding uplink resource assignment information; determines a size ofcontrol information, which has been adjusted by the base station suchthat when at least one of (i) a number of antenna port(s) of thecommunication apparatus and (ii) a number of antenna port(s) of the basestation is one, a size of the second control information with a formatincluding no precoding matrix indicator (PMI) has been adjusted by thebase station as being equal to a size of the first control informationwith a format including no PMI, and a size of the second controlinformation with a format including the PMI has been adjusted by thebase station as being different from a size of the first controlinformation; and detects whether the control information is addressed tothe communication apparatus or not based on the determined size ofcontrol information and detects whether the control information is thefirst control information or the second control information.
 11. Theintegrated circuit according to claim 10, comprising: at least one inputcoupled to the circuitry, wherein the at least one input, in operation,inputs data; and at least one output coupled to the circuitry, whereinthe at least one output, in operation, outputs data.
 12. The integratedcircuit according to claim 10, wherein when a transmission is performedusing one antenna port or when a diversity transmission is performed,the format including no PMI is used.
 13. The integrated circuitaccording to claim 10, wherein the format including no PMI for thesecond control information is a Format 0, and the format including noPMI for the first control information is a Format 1A.
 14. The integratedcircuit according to claim 10, wherein the circuitry, in operation,determines a larger one of a size of the first control information withthe format including no PMI and a size of the second control informationwith the format including no PMI as the size of the control information.15. The integrated circuit according to claim 10, wherein when atransmission with directivity control is performed, the format includingPMI is used for the second control information.
 16. The integratedcircuit according to claim 10, wherein the circuitry, in operation,determines the size of the second control information with the formatincluding PMI from an uplink bandwidth.
 17. The integrated circuitaccording to claim 10, wherein the circuitry, in operation, determinesthe size of the first control information with the format including PMIfrom a downlink bandwidth.
 18. The integrated circuit according to claim11, wherein the at least one output and the at least one input, inoperation, are coupled to an antenna.